Hidden spy cameras are a growing worldwide threat to people’s intimacy and privacy. With the growing interest in full-screen devices and the underlying development of under-screen cameras, a new type of potential security risk is introduced. Recent smartphones such as the ZTE AXON 40 already demonstrate that it’s infeasible to detect the camera with the human eye. There exist several techniques to detect hidden cameras, however most of these techniques are not resilient to the unique deployment scenario of the under-screen camera. A recent optical detection technique, which relies on the retro-reflective effect of hidden cameras, is promising but is also greatly hindered by challenges introduced due to reflections from the screen that is placed in front of the under-screen camera. In this work, these challenges are addressed, by proposing a detection principle that exploits the difference in reflective nature between the USC and the screen. Using reflection detection in a sliding window approach, a detection methodology is given to detect the USC. Furthermore, a detection architecture is designed that incorporates the proposed detection principles using a combination of computer vision, image processing and machine learning techniques. Using an off-the-shelf Time-of-Flight sensor, this architecture is implemented into a detection system and evaluated on its robustness and detection accuracy. Experiments on a dataset of 200 videos with a variety of measurement conditions show that this detection system is capable of achieving a USC detection rate of 71.5% while having a false-positive rate of 21.5%. It also proves excellent results while the screen is displaying content. ... Read more

In this thesis, a new RF Power Amplifier design is proposed that targets for improving the efficiency profile of classical RF Amplifiers. This RF Power Amplifier is especially designed for modulation schemes that need a PA with high PAPR. The PA consists of two different stages that will be digitally controlled. One of these stages has an optimized efficiency profile for supporting input signals with nominal power and the other stage has an optimized efficiency profile for supporting input signals with peak power. The PA has been designed with GaN HEMT's which perform very well at high frequencies while delivering high power.

The PA has been designed to perform optimally for frequencies around 100 MHz. Simulations show that at peak power, which is 40 dBm for this amplifier design, the PA has an efficiency of 63.5%. At 6 dB power back-off, the PA has an efficiency of 65.5%. The PA has a gain of approximately 20 dB at peak power level and approximately 18 dB at nominal power level. Furthermore the stability of the PA is optimized for the carrier frequency of the input signal. At 100 MHz the Rollet Stability Factor K is of magnitudes higher than unity which guarantees the stability of the circuit.

Furthermore a PCB has been developed to do some investigations in how this new PA design will perform in practice. Measurements on this PCB show that in power back-off a maximum efficiency of 63% can be reached. Results of the performance at peak power show that the efficiency reaches a maximum level of 37%. A possible reason for this is insufficient suppression of undesired harmonics. ... Read more